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Dr. Alan Greene on Lyme Disease


Our son was recently bitten by a tick. We're worried about Lyme disease. Can you tell us what we need to know?


Lyme disease is caused by a bacteria that lives in deer and white-footed mice, which do not develop the illness. When a tick feeds on the blood of one of these animals, it may become infected.

When an infected tick lands on someone, the bacteria are injected into the bloodstream through the saliva of the tick or deposited on the skin in tick feces. Thankfully, most ticks are not infected. Furthermore, it takes hours for the mouth parts of a tick to plant fully in the skin and much longer (days) for the tick to feed. Experiments have shown that it takes about 48 hours of feeding before the risk becomes substantial.

The symptoms of Lyme disease can be divided into three stages. In the first stage a characteristic skin rash is the most prominent feature; in the second cardiac and neurologic findings predominate; and in the third stage arthritis is the classic symptom.

The classic early manifestation of Lyme disease is a round rash that looks like a bull's-eye. The rash usually occurs at the site of the bite 7 to 14 days after the tick bite, though it has occurred as early as three days and as long as 32 days later. Without treatment the rash gradually expands to an average of 16 centimeters in diameter, but may be as large as 68 centimeters. The rash remains present for at least one to two weeks and usually twice that. At this stage, treatment is very simple, with amoxicillin or doxycycline. The symptoms usually resolve within several days. People with the skin lesions may have no other symptoms, but may also feel fatigue, headache, stiff neck, joint aches and pains, sometimes nausea, vomiting, and sore throat. There is often a low-grade fever, but it can be as high as 104 degrees with chills.

Neurologic abnormalities occur roughly four weeks after the tick bite, but they can occur as early as two weeks after the bite and up to months or even years later with a wide spectrum of involvement. It may be something as mild as meningeal irritation and headache, but can be as severe as meningitis, encephalitis, chorea, and demyelination. Cardiac abnormalities occur in only about 10 percent of patients, averaging five weeks after the tick bite and thankfully are relatively brief, lasting no longer than six weeks.

The arthritis of the third stage usually begins five to six weeks after the bite, although it may occur as early as one week afterwards or as late as many months later. Large joints, often those closest to the initial rash, are affected most commonly.

Diagnosis of Lyme disease is indicated by the appearance of a rash and/or flulike illness in the summer. The diagnosis is confirmed by blood tests, although false negative and false positive blood tests are common.

Should you try to save the tick? It's a good idea to bring the tick to your pediatrician or the public health department for visual identification. The current recommendation, however, is not to have all ticks actually tested for the Lyme bacteria, since even if present there is at least a 90 percent chance that the bitten person would not have contracted the disease.

Should everyone who is bitten get amoxicillin "just in case"? Experts have worked out what would happen if everyone who was bitten by a tick were to receive amoxicillin. Even though amoxicillin is a gentle antibiotic, there would be more suffering from side effects and allergic reactions than the suffering it would prevent by getting a jump start on treating those who actually have Lyme disease. It's better to wait for the first signs and symptoms before treating.

There is a widespread misconception that Lyme disease is difficult to eradicate completely, once the chronic symptoms have appeared. This is not the case. Most cases of treatment failure have later turned out to be among patients who did not actually have Lyme disease. The prognosis for children treated for Lyme disease is excellent no matter at which stage treatment is begun. Still, if caught in the first stage, symptoms usually resolve within days, and if caught in later stages the symptoms themselves may not resolve for 12 to 16 months after treatment is begun.

In December 1998, a Lyme disease vaccine was approved by the FDA for people 15 to 70 years of age. Those who visit or live in areas of high or moderate risk and whose activities result in exposure to vector ticks should discuss the possibility of vaccination with their physicians.


The information on this Web site is designed for educational purposes only. It is not intended to be a substitute for informed medical advice or care. You should not use this information to diagnose or treat any health problems or illnesses without consulting your pediatrician or family doctor. Please consult a doctor with any questions or concerns you might have regarding your or your child's condition.